The present invention relates to an apparatus for stuffer box crimping a synthetic multifilament yarn, as well as a method of stuffer box crimping a synthetic yarn. An apparatus and method of this general type are known from DE 26 32 082.
In the stuffer box crimping process, a multifilament yarn is advanced by means of a conveying nozzle into a stuffer box, compressed to a yarn plug and thereby crimped. To this end, the conveying nozzle receives a conveying medium, preferably a hot gas, which advances the yarn inside a yarn channel to the stuffer box. Inside the stuffer box, the yarn forms a plug. In so doing, the yarn comes to lie in loops on the surface of the yarn plug, and it is compressed by the conveying medium that is allowed to escape from the stuffer box through slots upstream of the yarn plug. Subsequently, the yarn plug is guided out of the stuffer box and cooled by means of a cooling device downstream thereof. After cooling, the yarn plug is disentangled to a form crimped yarn.
The crimp in the yarn is influenced in its intensity primarily by the plug formation and by the thermal treatment of the yarn plug. To form the yarn plug in the stuffer box, a cohesive force or counteracting force on the yarn plug is therefore generated in a direction opposite to the pressure of the conveying medium. To make it possible that the formation and treatment of the yarn plug is as constant as possible, it is now necessary to maintain a certain ratio of the conveying pressure to the counteracting force.
DE 26 32 082 and U.S. Pat. No. 4,301,578 disclose an apparatus and a method, wherein the counteracting force is determined from the friction between the yarn plug and the stuffer box wall, as well as from the conveying speed of a pair of rolls arranged at the outlet of the stuffer box. In this apparatus and method, the problem arises that as running time increases, the surfaces of the stuffer box wall change in their frictional behavior due to wear, which is bound to entail a change in the counteracting force.
EP 0 554 642 and U.S. Pat. No. 5,351,374 disclose, for example, an apparatus, wherein the counteracting force for forming a plug results exclusively from the friction between the plug and the stuffer box. However, this leads to a change in the counteracting force after a short running time. Constant measures of adaptation are in this instance unavoidable.
It is therefore the object of the invention to improve the known apparatus and the known method for stuffer box crimping a synthetic multifilament yarn such that they ensure a uniform formation of the yarn plug and a uniform thermal treatment of the yarn plug.
A further object of the invention it to produce a lintfree filament assembly.